What speed will an object fall?

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In summary, the speed an object falls is independent of its weight, but only if the effects of drag are ignored. The equation for constant acceleration is well-known and can be derived using the formula 0.5mv^2=mgh. The speed of an object falling from a known height and weight can be calculated using the formula v=(2gh)^0.5. However, this formula is only accurate if the effects of drag are ignored, which is not the case in real life.
  • #1
ATCLanser
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I am looking for a formula to determine what speed an object will fall with a known height and weight. For example a 220 pound man falls from 65 ft, what speed will he be going when he hits the ground?
 
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  • #2
You do know that the speed an object falls is independent of its weight...right? The equations for constant acceleration are very well known in intro physics courses.

http://selland.boisestate.edu/jbrennan/physics/notes/Motion/constant_acceleration_formulas.htm [Broken]

http://www.juliantrubin.com/bigten/galileofallingbodies.html
 
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  • #3
FredGarvin said:
You do know that the speed an object falls is independent of its weight...right?
I know that you know this Fred, but for the benefit of the OP I will mention the caveat that an objects' instantaneous velocity is only independent of mass provided that the effects of drag are ignored.
 
  • #4
Hootenanny said:
I know that you know this Fred, but for the benefit of the OP I will mention the caveat that an objects' instantaneous velocity is only independent of mass provided that the effects of drag are ignored.
True. However it should be pointed out that drag is not proportional in any way to mass either. It is a function of geometry.
 
  • #5
ATCLanser said:
I am looking for a formula to determine what speed an object will fall with a known height and weight. For example a 220 pound man falls from 65 ft, what speed will he be going when he hits the ground?

There is a simple derivation for the formula below.
The kinetic energy at the moment the object hits the ground is 0.5mv^2 which is equal to its potential energy at given height "h"
Thus 0.5mv^2=mgh
And v=(2gh)^0.5 which is independant of the weight.
 
  • #6
aniketp said:
There is a simple derivation for the formula below.
The kinetic energy at the moment the object hits the ground is 0.5mv^2 which is equal to its potential energy at given height "h"
Thus 0.5mv^2=mgh
And v=(2gh)^0.5 which is independant of the weight.

This is only true if the drag force is ignored (as pointed out previously by Hootenanny and Fred). In real life it is not normally ignored.

CS
 

1. What is the acceleration of gravity?

The acceleration of gravity, denoted by g, is a constant value equal to 9.8 meters per second squared (m/s²) on Earth. This means that an object in free fall will accelerate at a rate of 9.8 m/s² towards the ground.

2. Does the weight of an object affect its falling speed?

Yes, the weight of an object does affect its falling speed. Heavier objects have a greater force of gravity acting on them, so they will accelerate faster than lighter objects. However, in a vacuum where there is no air resistance, all objects will accelerate at the same rate regardless of their weight.

3. What factors can affect the speed at which an object falls?

The speed at which an object falls can be affected by several factors, including the object's mass, air resistance, and gravitational pull. In addition, the height from which the object is dropped and the medium through which it is falling can also impact its speed.

4. Can an object fall faster than the acceleration of gravity?

No, an object cannot fall faster than the acceleration of gravity. This is because the acceleration of gravity is a constant value and is the maximum speed an object can reach while falling. However, an object can reach this speed in different amounts of time depending on the factors mentioned above.

5. How can the speed of an object falling be calculated?

The speed of an object falling can be calculated using the equation v = gt, where v is the final velocity, g is the acceleration of gravity, and t is the time it takes for the object to fall. This equation assumes that there is no initial velocity and no air resistance. If air resistance is present, a more complex equation is needed to calculate the speed of the falling object.

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